U.S. patent application number 10/572375 was filed with the patent office on 2006-12-21 for method of forming monodisperse bubble.
This patent application is currently assigned to Miyazaki Prefecture. Invention is credited to Yasuaki Kohama, Masato Kukizaki, Tadao Nakashima.
Application Number | 20060284325 10/572375 |
Document ID | / |
Family ID | 34675173 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060284325 |
Kind Code |
A1 |
Kohama; Yasuaki ; et
al. |
December 21, 2006 |
Method of forming monodisperse bubble
Abstract
The invention provides a method for producing bubbles that
exhibit an excellent monodispersity. The invention relates to a
method for generating bubbles by the injection and dispersion of a
gas through a porous body into a liquid, wherein the value produced
by dividing the pore diameter that accounts for 10% of the total
pore volume in the relative cumulative pore distribution curve of
the porous body by the pore diameter that accounts for 90% of the
total pore volume in the relative cumulative pore dismeter
distribution curve of the porous body is 1 to 1.5.
Inventors: |
Kohama; Yasuaki; (Miyagi,
JP) ; Kukizaki; Masato; (Miyazaki, JP) ;
Nakashima; Tadao; (Miyazaki, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
Miyazaki Prefecture
Miyazaki-shi
JP
Yasuaki Kohama
Sendai-shi
JP
|
Family ID: |
34675173 |
Appl. No.: |
10/572375 |
Filed: |
December 13, 2004 |
PCT Filed: |
December 13, 2004 |
PCT NO: |
PCT/JP04/18558 |
371 Date: |
March 16, 2006 |
Current U.S.
Class: |
261/122.1 ;
261/DIG.26 |
Current CPC
Class: |
B01F 3/04262 20130101;
Y10S 261/26 20130101 |
Class at
Publication: |
261/122.1 ;
261/DIG.026 |
International
Class: |
B01F 3/04 20060101
B01F003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2003 |
JP |
2003 416945 |
Claims
1. A method for producing bubbles by the injection and dispersion
of a gas through a porous body into a liquid, wherein the porous
body has a value of 1 to 1.5, wherein the value is given by
dividing the pore diameter that accounts for 10% of the total pore
volume in the relative cumulative pore distribution curve of the
porous body by the pore diameter that accounts for 90% of the total
pore volume in the relative cumulative pore diameter distribution
curve of the porous body.
2. The method according to claim 1, wherein the contact angle with
respect to the liquid of at least the surface of the porous body
that is in contact with the liquid is greater than 0.degree. and
less than 90.degree..
3. The method according to claim 1, wherein porous glass is used as
the porous body.
4. The method according to claim 1, wherein the liquid contains at
least one additive selected from the group consisting of
emulsifying agents, emulsion stabilizers, foaming agents, and
alcohols.
5. Bubbles obtained by the method according to claim 1.
6. The bubbles according to claim 5, wherein, in the integrated
volume distribution of the bubbles, 1) the diameter at which the
bubble volume accounts for 10% of the total bubble volume is at
least 0.5-times the diameter at which the bubble volume accounts
for 50% of the total bubble volume, and 2) the diameter at which
the bubble volume accounts for 90% of the total bubble volume is no
more than 1.5-times the diameter at which the bubble volume
accounts for 50% of the total bubble volume.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing
monodisperse bubbles.
BACKGROUND ART
[0002] Various methods for generating bubbles have already been
proposed. Examples in this regard are a) gas transport methods in
which a gas is passed through the micropores of a gas dispersing
tube into a liquid; b) methods in which a vibration with a
frequency no greater than 1 kHz is applied to a porous body while a
gas is being fed into a liquid through the porous body; c) bubble
generation methods that utilize ultrasound; d) shakingstirring
methods in which bubbles are generated by stirring a liquid and
shearing a gas; e) methods in which a gas is dissolved under
pressure in a liquid followed by pressure reduction in order to
generate bubbles from the supersaturated dissolved gas; and f)
chemical foaming methods in which bubbles are created by generating
a gas in a liquid by a chemical reaction (refer, for example, to
Clift, R. et al., "Bubbles, Drops, and Particles", Academic Press
(1978), and Hideki TAKUSHOKU, "Progress in Chemical Engineering.
16. Bubble, Drop, and Dispersion Engineering", Maki Shoten, 1
(1982)).
[0003] However, these methods, excluding methods that generate
microfine bubbles utilizing microwaves, not only have difficulty
producing very fine bubbles with bubble diameters on the order of
nanometers, but also suffer from the problem of an impaired
stability due to a nonuniform bubble diameter. In addition, it is
also extremely difficult in the aforementioned methods to freely
adjust the bubble diameter.
DISCLOSURE OF THE INVENTION
[0004] A main object of this invention is to provide a method for
generating bubbles that exhibit an excellent monodispersity.
[0005] As a result of extensive and focused investigations, the
inventor discovered that this object could be achieved by applying
pressure to a gas and dispersing it into a liquid through a special
porous body. This invention was achieved based on this
discovery.
[0006] That is, the present invention relates to the following
method for preparing bubbles.
[0007] 1. A method for producing bubbles by the injection and
dispersion of a gas through a porous body into a liquid,
[0008] wherein the porous body has a value of 1 to 1.5,
[0009] wherein the value is given by dividing the pore diameter
that accounts for 10% of the total pore volume in the relative
cumulative pore distribution curve of the porous body by the pore
diameter that accounts for 90% of the total pore volume in the
relative cumulative pore diameter distribution curve of the porous
body.
[0010] 2. The method according to above 1, wherein the contact
angle with respect to the liquid of at least the surface of the
porous body that is in contact with the liquid is greater than
0.degree. and less than 90.degree..
[0011] 3. The method according to above 1, wherein porous glass is
used as the porous body.
[0012] 4. The method according to above 1, wherein the liquid
contains at least one additive selected from the group consisting
of emulsifying agents, emulsion stabilizers, foaming agents, and
alcohols.
[0013] 5. Bubbles obtained by the method according to above 1.
[0014] 6. The bubbles according to above 5, wherein, in the
integrated volume distribution of the bubbles,
[0015] 1) the diameter at which the bubble volume accounts for 10%
of the total bubble volume is at least 0.5-times the diameter at
which the bubble volume accounts for 50% of the total bubble
volume, and
[0016] 2) the diameter at which the bubble volume accounts for 90%
of the total bubble volume is no more than 1.5-times the diameter
at which the bubble volume accounts for 50% of the total bubble
volume.
ADVANTAGES OF THE INVENTION
[0017] The method according to the present invention can reliably
produce highly monodisperse bubbles. The method according to the
present invention in particular can also provide microfine
monodisperse bubbles for which the bubble diameter size is in the
nanometer range (monodisperse nanobubbles). In addition, the method
according to the present invention also enables the bubble diameter
to be freely adjusted by varying, for example, the pore diameter of
the porous body.
[0018] The monodisperse bubbles and particularly the nanobubbles
and/or microbubbles (microfine monodisperse bubbles for which the
bubble diameter size is in the micrometer range) obtained by the
method according to the present invention can be used in a broad
range of fields, such as hydroponic cultivation, the cultivation of
marine products, bubble-containing food products, microcapsules,
pharmaceutical preparations and cosmetics, various foam materials,
and separation processes such as ore flotation and bubble-utilizing
foam separation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic diagram that shows an example of an
apparatus for executing the method according to the present
invention.
[0020] FIG. 2 is a schematic diagram of a bubble-generating
apparatus.
[0021] FIG. 3 shows the bubble diameter distribution of the
nanobubbles obtained in Example 1.
[0022] FIG. 4 shows the relationship between the average pore
diameter of a porous glass membrane and the average bubble
diameter.
[0023] FIG. 5 shows the relationship between the critical pressure
and the average pore diameter of a porous glass membrane.
BEST MODE FOR CARRYING OUT THE INVENTION
[0024] The method according to the present invention for producing
bubbles is a method for producing bubbles by the injection and
dispersion of a gas through a porous body into a liquid,
[0025] wherein the porous body has a value of 1 to 1.5,
[0026] wherein the value is given by dividing the pore diameter
that accounts for 10% of the total pore volume in the relative
cumulative pore distribution curve of the porous body by the pore
diameter that accounts for 90% of the total pore volume in the
relative cumulative pore diameter distribution curve of the porous
body.
[0027] As used hereinbelow with reference to the present invention,
the "10% diameter" refers to the pore diameter that accounts for
10% of the total pore volume in the relative cumulative pore
distribution curve of the porous body while the "90% diameter"
refers to the pore diameter that accounts for 90% of the total pore
volume in the relative cumulative pore diameter distribution curve
of the porous body.
[0028] The Porous Body
[0029] The porous body used by the method according to the present
invention has a relative cumulative pore diameter distribution
curve in which the value given by dividing the 10% diameter by the
90% diameter is 1 to 1.5 and preferably 1.2 to 1.4. The use of a
porous body having a pore diameter distribution in this range (that
is, a porous body with a uniform pore diameter) enables the
reliable production of bubbles that exhibit an excellent
monodispersity.
[0030] The pore diameter of the porous is not specifically
restricted, but can generally be set upon as appropriate from
within the average pore diameter range of 0.02 to 25 .mu.m
(preferably 0.05 to 20 .mu.m). The average bubble diameter of the
monodisperse bubbles can also be freely adjusted in particular
within the range of about 0.2 to 200 .mu.m by adjusting the pore
diameter.
[0031] The porous body can be any porous body that has a uniform
pore diameter as defined hereinabove. The pore shape is not
particularly limited as long as the pore shape is that of a through
pore, and the pore shape can be exemplified by a cylindrical
column, a square column, and so forth. The pores can run through
perpendicular to the surface of the porous body or can run through
obliquely, and the pores can be intertwined with each other. The
pores in the porous body preferably have a uniform hydraulic
diameter. Such a pore structure is very suitable for use by this
invention.
[0032] The shape of the porous body is also not limited and may be
any shape capable of dispersing a gas into a liquid. The porous
body can be, for example, membrane shaped, block shaped, disk
shaped, square column shaped, cylindrical column shaped, and so
forth. This can be selected as appropriate in accordance with the
intended use, service, and so forth. A membrane-shaped porous body
can generally be suitably used. A membrane-shaped porous body can
have the shape of a flat membrane or a pipe. In addition, a
membrane-shaped porous body can be a symmetric membrane or an
asymmetric membrane. Moreover, a membrane-shaped porous body can be
a uniform or nonuniform membrane. These shapes and structures are
selected as appropriate in correspondence to the type of liquid
used, the intended bubbles, and so forth.
[0033] The size of the porous body is also not limited and can be
selected as appropriate in view of the bubble generation
application, the method of using the porous body, and so forth.
[0034] The material constituting the porous body is also not
limited and can be selected as appropriate. Preferred materials can
be exemplified by glasses, ceramics, silicon, polymers, or the
like. Glasses (porous glasses) in particular can be suitably used
by the present invention. Suitable for use as the porous glass is,
for example, porous glass produced utilizing microphase separation
in glass. The known porous glasses can be used as such porous
glass, and, for example, porous glasses produced utilizing
microphase separation in glass can be suitably used. Specific
examples are the CaO--B2O3-SiO2-Al2O3-based porous glass disclosed
in Japanese Patent 1,504,002 and the
CaO--B2O3-SiO2-Al2O3-NaO2-based porous glass and
CaO--B2O3-SiO2-Al2O3-NaO2-MgO-based porous glass disclosed in
Japanese Patent 1,518,989 and U.S. Pat. No. 4,657,875. Also usable
is the SiO2-ZrO2-Al2O3-B2O3-NaO2-CaO-based porous glass disclosed
in Japanese Published Patent Application No. 2002-160941.
[0035] The porous body in the present invention desirably exhibits
good wetting by the liquid used. Porous bodies that are either
poorly wetted or not wetted by the liquid used can also be used
after execution thereon of a surface treatment or surface
modification by a known method so as to be wettable by the liquid
used. Wetting by the liquid denotes a contact angle by the liquid
on the surface of the porous body preferably greater than 0.degree.
and less than 90.degree., particularly preferably greater than
0.degree. and less than 45.degree., and more preferably greater
than 0.degree. and no greater than 30.degree..
[0036] The Gas
[0037] There are no particular limitations on the gas used by the
present invention, and a desired gas can be used as appropriate.
The gas used by the present invention can be exemplified by at
least one selection from the group consisting of substances that
are gases at ambient temperature, such as air, nitrogen gas, oxygen
gas, ozone gas, carbon dioxide, methane, hydrogen gas, ammonia, and
hydrogen sulfide, and the vapors of substances that are liquid at
ambient temperature, such as ethyl alcohol, water, and hexane.
[0038] The Liquid
[0039] There are also no particular restrictions on the liquid used
by the present invention, and a variety of liquids can be used. The
liquid used by the present invention can be exemplified by water
and by oil-miscible liquids such as oils, fats, and organic
solvents.
[0040] An additive can also be added to the liquid in the present
invention in order to stabilize the obtained bubbles. Preferred for
use as the additive is at least one selection from emulsifying
agents, emulsion stabilizers, foaming agents, and alcohols.
[0041] The emulsifying agent can be any emulsifying agent that has
the ability to lower the interfacial tension of the liquid, and
known emulsifying agents and commercial products can be used. In
addition, either a water-soluble emulsifying agent or an oily
emulsifying agent can be used as the emulsifying agent.
[0042] The known hydrophilic emulsifying agents can be used as the
water-soluble emulsifying agent. For example, nonionic emulsifying
agents can be exemplified by glycerol fatty acid esters, sucrose
fatty acid esters, sorbitan fatty acid esters, polyglycerol fatty
acid esters, polyoxyethylene hydrogenated castor oil,
polyoxyethylene-polyoxypropylene glycols, lecithin, and polymeric
emulsifying agents. The anionic emulsifying agents can be
exemplified by carboxylic acid salts, sulfonic acid salts, and
sulfate ester salts. The HLB of these hydrophilic emulsifying
agents is preferably at least 8.0 and more preferably is at least
10.0 These hydrophilic emulsifying agents can be used individually
or in combinations of two or more in correspondence to the desired
emulsifying activity. The quantity of addition of these hydrophilic
emulsifying agents is not specifically limited as long as an
adequate emulsifying effect is obtained; generally, however, about
0.05 to 1 weight % with reference to the emulsion as a whole will
be appropriate.
[0043] Nonionic emulsifying agents, for example, can be used as the
oily emulsifying agent. More specific examples are glycerol fatty
acid esters, sucrose fatty acid esters, sorbitan fatty acid esters,
propylene glycol fatty acid esters, polyglycerol fatty acid esters,
polyoxyethylene hydrogenated castor oil,
polyoxyethylene-polyoxypropylene glycols, lecithin, and so forth.
These can be used individually or two or more can be used.
Particularly preferred among the preceding are polyglycerol fatty
acid esters, sucrose fatty acid esters, and so forth. The quantity
of addition of the oily emulsifying agent can be determined as
appropriate in view, inter alia, of the type of oily emulsifying
agent used; generally, however, about 0.05 to 30 weight % in the
liquid is appropriate.
[0044] The emulsion stabilizer is a substance that coats the
gas-liquid interface of the generated bubbles and thereby
stabilizes the bubbles. The emulsion stabilizer can be exemplified
by synthetic polymers such as polyvinyl alcohol and polyethylene
glycol. Its quantity of addition is not particularly limited as
long as a satisfactory bubble-generating effect is obtained;
generally, however, about 0.05 to 50 weight % in the liquid is
appropriate.
[0045] The foaming agent is a substance that can facilitate bubble
generation, but is not otherwise limited. The foaming agent can be
exemplified by glycosides such as saponins; polysaccharides such as
sodium alginate and carrageenan; and proteins such as albumin and
casein. The quantity of addition is not limited as long as a
satisfactory bubble-generating effect is obtained; generally,
however, about 0.05 to 50 weight % in the liquid is
appropriate.
[0046] The alcohol can be exemplified by ethyl alcohol, propyl
alcohol, and butanol. Addition of the alcohol facilitates bubble
generation by reducing the interfacial tension y of the liquid. The
quantity of alcohol addition is not particularly limited as long as
an adequate bubble-generating effect is obtained; generally,
however, about 0.05 to 50 weight % in the liquid is
appropriate.
[0047] The method for generating monodisperse bubbles The method
according to the present invention generates bubbles by the
injection and dispersion of a gas through the porous body described
hereinabove into a liquid.
[0048] There are no particular limitations on the procedure for
injection and dispersion. Injection and dispersion can be carried
out, for example, as follows. First, a side of the porous body is
brought into contact with a liquid and another side is brought into
contact with a gas. Then, by pressurizing the gas, the gas is
caused to traverse the through pores of the porous body and to
disperse into the liquid. Methods for pressurizing the gas can be
exemplified by methods in which the gas is forcibly filled into a
sealed space and methods in which the gas is filled into a sealed
space and the air is thereafter compressed with, for example, a
piston.
[0049] An example of a preferred embodiment of the execution of the
method according to the present invention is provided hereafter. A
liquid (c) is transported to a porous glass membrane and membrane
module (a) by a pump (d). A gas in a gas cylinder (b) is
transported to the porous glass membrane and membrane module (a)
under regulation by a valve (e) while referring to a pressure gauge
(f). Proceeding in this manner enables the dispersion of bubbles in
the liquid. The particle diameters of the obtained bubbles can be
measured by a particle size distribution analyzer based on the
laser diffraction method (g).
[0050] FIG. 2 is a schematic diagram of bubble generation at the
porous body when the gas is pressurized. The pressure difference
.DELTA.P (=PA-PL) between the pressure PA of the gas when the gas
is pressurized and the pressure PL of the liquid is generally given
by the following equation; .DELTA.P=4.gamma. cos .theta./Dm
[0051] wherein .gamma. is the surface tension of the liquid
relative to the gas, .theta. is the angle of contact relative to
air of the is liquid present at the surface of the porous body, and
Dm is the average pore diameter of the porous body.
[0052] In the present invention, in order to obtain monodisperse
bubbles having a smaller average bubble diameter, .DELTA.P is
desirably controlled to about 0.2 to 10 MPa and particularly about
1 to 5 MPa.
[0053] Bubble generation may be carried out by the present
invention according to either a batch or continuous regime. The
continuous regime, when used, is desirably carried out as follows.
When, for example, the porous body is a flat membrane, the liquid
is preferably stirred with, for example, a stirrer. When, for
example, the porous body is a tubular membrane, the liquid is
preferably circulated using a pump. The particle diameter of the
obtained monodisperse bubbles can be measured by known methods
using commercially available particle diameter measurement
instruments.
[0054] The Bubbles
[0055] The bubbles obtained by the method according to the present
invention (bubbles according to the present invention) in general
have small bubble diameters and are monodisperse. In particular,
the bubbles have a high monodispersity that, in the cumulative
volume distribution of the bubbles, the diameter at which the
bubble volume accounts for 10% of the total bubble volume is at
least 0.5-times (preferably about 0.6- to 0.8-times) the diameter
at which the bubble volume accounts for 50% and the diameter at
which the bubble volume accounts for 90% of the total bubble volume
is no more than 1.5-times (preferably about 0.2- to 1.4-times) the
diameter at which the bubble volume accounts for 50%.
[0056] While there is no limitation on the average bubble diameter
of the bubbles according to the present invention, this value is
ordinarily about 0.2 to 200 .mu.m and can be decided upon as
appropriate in correspondence to the specific application and so
forth. In particular, the bubble diameter of the bubbles can be
controlled into a freely selected range in the method according to
the present invention by altering the pore diameter of the porous
body used. The method according to the present invention can also
produce, for example, 400 nm to 900 nm nanobubbles.
[0057] The bubbles according to the present invention can be used
in a variety of applications, such as in the medical field and for
agricultural chemicals, cosmetics, food products, and so forth.
With regard to medical applications, the bubbles according to the
present invention can specifically be used in contrast media and
drug delivery system (DDS) formulations. When nanobubbles are
incorporated into the contrast media used in ultrasound diagnosis,
the sensitivity of the contrast media is dramatically improved due
to the fact that the bubbles exhibit a unique sensitization action
with respect to ultrasound. In addition, the introduction of
bubbles into microcapsules also makes it possible to rupture the
microcapsules at a target region by exposure to shock waves and
thereby release a drug present in the capsule.
[0058] In the field of food products, the stability of the
monodisperse nanobubbles or monodisperse microbubbles can be used
to improve the texture and taste of, for example, mousse food
products. In addition, by injecting nanobubbles of an inert gas
such as nitrogen into a beverage, such as milk or PET bottle or bag
tea, the dissolved oxygen that is a cause of beverage deterioration
can be very efficiently removed, thereby enabling an inhibition of
quality deterioration.
[0059] With regard to cosmetic applications, the stability of the
monodisperse nanobubbles or monodisperse microbubbles enables use
as a high-quality mousse (hair setting materials, skin cream, and
so forth).
[0060] With regard to biological and chemical applications, the
invention can be very suitably used in hydroponic cultivation,
marine cultivation, and so forth, by utilizing the very large
surface area of nanobubbles and microbubbles for the dissolution of
oxygen in water. In addition, water can also be sterilized very
efficiently using ozone nanobubbles. Moreover, because nanobubbles
and microbubbles exhibit a binding activity for substances present
in the liquid, due to their large surface area they can very
efficiently inhibit the proliferation of microorganisms
(antimicrobial activity) and can very efficiently effect the
separation and recovery of suspended material (ore flotation and
foam separation).
[0061] Otherwise, bringing the body into contact with nanobubbles
or microbubbles at, for example, a bathhouse or hot spring,
provides better stimulation of blood flow, a better temperature
maintenance effect, a better skin reviving effect, and so
forth.
EXAMPLES
[0062] The invention is described in additional detail hereinbelow
through examples. However, the scope of the invention is not
limited to these examples.
Example 1
[0063] Using the apparatus shown in FIG. 1, air was injected and
dispersed through a tubular porous glass membrane having an average
pore diameter of 85 nm (SPG membrane from SPG Technology Co., Ltd.)
into an aqueous solution containing 0.1 weight % anionic
emulsifying agent (sodium dodecyl sulfate). The pressure difference
.DELTA.P between the air and the aqueous solution was 3.0 MPa and
the liquid temperature was 25.degree. C. The aqueous solution was
transported by a pump and the in-tube flow velocity within the
membrane was set at 4.0 m/s.
[0064] The generated bubbles were directly introduced into the
measurement cell of a particle diameter distribution measurement
instrument (product name: "SALD2000", from the Shimadzu
Corporation). The obtained bubble diameter distribution is shown in
FIG. 3. As is clear from FIG. 3, the obtained bubbles were highly
monodisperse nanobubbles having an average bubble diameter of 750
nm.
Example 2
[0065] The relationship between the pore diameter of the porous
glass membrane and the average bubble diameter of the generated
bubbles was investigated in accordance with Example 1 by varying
the average pore diameter of the porous glass membrane. The results
are shown in FIG. 4. As is clear from FIG. 4, a linear relationship
given by Dp=8.6 Dm exists between the average bubble diameter Dp
and the average pore diameter Dm.
Example 3
[0066] The relationship for the minimum pressure .DELTA.Pc
(critical pressure) at which bubble generation began for different
average pore diameters in the porous glass membrane was
investigated in accordance with Example 1 by varying the average
pore diameter of the porous glass membrane. The results are shown
in FIG. 5. The relationship between .DELTA.P and Dm was in
approximate agreement with the equation shown above by (1)
.DELTA.P=4.gamma. cos .theta./Dm.
Example 4
[0067] The contact angle .theta. between the aqueous phase and the
porous glass membrane used in Example 1 was measured by the
liquid-capillary-rising method (Yazawa, T., H. Nakamichi, H. Tanaka
and K. Eguchi; "Permeation of Liquid through Porous Glass Membrane
with Surface Modification," J. Ceram. Soc. Japan, 96, 18-23
(1988)). The result was a contact angle of .theta.=28.degree..
* * * * *